1. Field of the Invention
The present invention relates to a printing apparatus that prints an image on one side or both sides of a sheet, a control method for the printing apparatus, and a storage medium.
2. Description of the Related Art
In the related art, when double-sided printing is performed on recording paper (sheet), a double-sided circulation printing method is known in which, in order to enhance productivity, after image formation has been performed on first sides of several sheets, image formation is performed alternately on first and second sides of sheets (see Japanese Patent Publication No. 07-037304).
In recent years, many of image forming apparatuses, such as color copying machines which have rapidly come into widespread use, include photosensitive members and toner cartridges for four colors of yellow, magenta, cyan, and black.
In such an image forming apparatus, print image data is converted into recording laser beams for four colors, and the photosensitive members for the respective colors are irradiated with the respective recording laser beams to form respective electrostatic latent images thereon. Then, toner development is performed by using toner supplied from each toner cartridge, and primary transfer of visualized images is performed onto an intermediate transfer belt. Hereinafter, a series of processes from conversion of print image data to primary transfer is referred to as an imaging process.
Subsequently, a sheet starts to be fed from a sheet cassette. When the fed sheet reaches a position, which is a secondary transfer position, the toner images are transferred from the intermediate transfer belt onto the sheet. Toner on the sheet is fixed by a fixing unit applying pressure and heat thereto. In the case of double-sided printing, after toner has been fixed on a first side of a sheet, a conveying path is switched, and the sheet is switched back and then conveyed to a double-sided printing sheet conveying path.
Subsequently, as in the first side, an imaging process for a second side is performed, the sheet is re-fed from the double-sided printing sheet conveying path to the secondary transfer position, and secondary transfer and fixing of toner are performed. In the case where double-sided circulation printing is performed, a subsequent job waits to be input until a last sheet of a job reaches the double-sided printing sheet conveying path, thereby enhancing the total productivity of double-sided printing of jobs including the subsequent job.
However, when such double-sided circulation printing across a plurality of jobs is performed, the productivity of double-sided printing of jobs including a subsequent job increases, but completion of printing on a second side of a last sheet of a preceding job will be delayed. On the other hand, when double-sided circulation printing is performed so that it is not performed across a plurality of jobs, if a large number of double-sided print jobs in each of which a small number of pages are to be printed are input, the productivity of printing decreases significantly.